On the roof of the world, Chinese paramilitaries are trying to snuff out Tibetan resistance to Beijing's rule with spiked batons, semi-automatic weapons and fire extinguishers.

Every 20 metres along the main road of Aba, the remote town on the Tibetan plateau that is at the heart of the current wave of protests, police officers and communist officials wearing red armbands look out for potential protesters. Dozens more paramilitaries sit in ranks outside shops and restaurants in an intimidating show of force.

At the nearby Kirti monastery, Chinese officers in fire trucks keep a close eye on pilgrims prostrating themselves, in case their devotion turns to immolation.

Outsiders are not supposed to see this. The Chinese authorities have gone to great lengths to block access to Aba, in north-western Sichuan, which is home to more than half the 23 monks, nuns and lay Buddhists who have set fire to themselves in acts of defiance aimed at the Chinese Communist party in the past two years.

The authorities have blocked internet and mobile phone signals. Checkpoints have been set up on surrounding roads to keep outside observers, particularly foreign journalists, away.

But after a 10-hour drive through mountain valleys and snow-covered plains, the Guardian was able to get into Aba and witness how the authorities are trying to quell dissent with security, propaganda and "re-education" campaigns. These tactics have had little success. Despite flooding Aba with security personnel, the protests continue.

Such acts of suicide and self-mutilation are escalating and widening. According to exile groups, there have been 23 self-immolations in the past two years, including six in the past eight days. The Chinese government disputes the number but acknowledges more than a dozen cases, and has warned of further unrest.

The tension is rippling outwards. Last week, in the provincial capital Chengdu, armed riot police with fire extinguishers to hand watched the crowds in the main Chunxi shopping district. Out of their sight, a Tibetan monk from Qinghai said the situation had worsened. "Now is difficult for Tibetans. The controls are very strict. There are many more police."

In the city's Tibetan quarter, police patrol cars were parked every few dozen metres. Many locals felt intimidated. "It's difficult to talk. It's very sensitive. They say people have died," said one shopkeeper from Aba. Others in the area were desperate for information from locked-down areas on the Tibetan plateau.

"My mother, father and husband are still there. It's a worry. I haven't been able to call for more than a week," said a restaurant owner from Seda, where protests and self-immolations have also been reported. "The government says only one person was killed, but we heard dozens were taken away and we don't know what has happened to them."

With more demonstrations expected before the Tibetan new year next week, Chen Quanguo, the communist party chief of Tibet, told security personnel to ready themselves for "a war against secessionist sabotage," according to a recent article in the Tibet Daily.

The countermeasures appear to include the use of lethal force. Security forces shot and killed a Tibetan monk and his brother on Thursday, according to Free Tibet. Yeshe Rigsal and Yeshe Samdrub had reportedly been on the run for more than two weeks after participating in a protest in Draggo, in Ganzi (known in Tibetan as Kardze), calling for the return of the Dalai Lama.

Protests have broken out in several areas, but the most intense have been in Aba, known in Tibetan as Ngaba – a mountainous area of north-west Sichuan that has been resisting Chinese Communist party rule for decades. In the 1930s, Mao Zedong encountered opposition here during his Long March. In 2008, it was the scene of some of the bloodiest clashes with security personnel. And 13 of the current 23 self-immolations have occurred here.

Today, Aba has road blocks, spot checks and a security presence reminiscent of conflict zones in the Middle East or Northern Ireland.

But the violence here is, for the most part, self-inflicted. And the battle is not for territory, but for hearts and minds and beliefs.

Locals are under pressure to show loyalty to the authorities. Chinese flags fly on every building. Posters emphasise the need for stability and harmony to achieve economic development.

The Tibetan community is divided.

"We are all Buddhists, but I don't agree with the self-immolations. That is the act of extremists," said one monk on the road near Aba. "We need peace."

But others are frustrated as restrictions have tightened and the prospects of a negotiated settlement diminish.

There has been no dialogue between the Chinese government and emissaries of the Dalai Lama since 2010. Meanwhile, the authorities have stepped up security and controls on monasteries.

A major source of discontent has been the lengthy "re-education campaigns" imposed on monks, who are forced to publicly renounce the Dalai Lama as a reactionary traitor and profess their patriotism and loyalty to China.

"They call it re-education, but in reality it means threats and intimidation. Monks would rather die than accept this," said Kanyag Tsering, a monk who has been in exile for 13 years. "I am very concerned that if current policies continue unchanged, there will be a rise in self-immolation protest and even more terrifying forms of protest."

Aba has long had one of the densest concentrations of monks and monasteries on the Tibetan plateau. Because of its importance, it's been subject to a stranglehold, said Kate Saunders of the International Campaign for Tibet. "In Tibet, the monasteries serve the function of universities. What is happening now is like a military blockade of Oxford and Cambridge. It's as if the UK tried to prevent students from studying anything except what the government wanted them to study. There is no breathing space."

China says its measures are necessary because the unrest has been plotted by the Dalai Lama and his followers. "Because of the violent incidents of mobbing and smashing, the Chinese government has taken appropriate measures to meet the desire of Tibetan communities for stability," said foreign ministry spokesperson Liu Weimin. "The incidents in some areas do not affect the harmony and stability of ethnic groups in China."

The prospects for calm appear remote. A professor at the Minorities University – who asked to remain anonymous – said the security presence was greater this year than it was during the deadly uprisings of 2008. "There are serious problems in the relationship between Han and Tibetans. It has got worse these past four years," the professor said.